<?php
    header('Access-Control-Allow-Origin: *');
    header('Content-Type:text/html;charset=utf-8');
    $con = mysqli_connect("127.0.0.1", "root", "root", "mydb");
    $classId = $_GET['classId'];
    $sql = "UPDATE lesson SET isSign = 0, signPwd = null, sign_location=null WHERE l_id = '$classId';";
    $res = mysqli_query($con,$sql);
    if(mysqli_affected_rows($con) > 0){
        echo 'close';
    }else{
        echo 'fail';
    }
    mysqli_close($con);
?>